1. Field of the Invention
The present invention relates to a wire electric discharge machine, and more particularly, to a wire electric discharge machine having a function to determine whether or not electrical discharge machining of a workpiece can be performed.
2. Description of the Related Art
In recent years, various metal materials have been developed. In the part of the metal materials, there is also a metal material of which electrical conductivity is very low and electrical discharge machining cannot be performed. Meanwhile, materials having high electrical conductivity also have been developed among ceramic materials and organic compound materials that have been treated as insulating materials until now. It is very difficult for a general user to determine whether or not the electrical discharge machining of these materials can be performed at a glance.
In the related art, a user measures a resistance value or electrical conductivity by using a measuring instrument such as a tester in order to determine whether or not the electrical discharge machining of a workpiece as an object can be performed, and determines that the electrical discharge machining of the workpiece can be performed when a resistance value is low or electrical conductivity is high (for example, paragraph [0033] of JP 11-320258 A).
However, since a threshold of a resistance value or electrical conductivity at which electrical discharge machining can be performed varies depending on the characteristics and the like of a power supply of the wire electric discharge machine, there is a case in which wire electrical discharge machining can be performed even though specific resistance is somewhat low. For this reason, it is possible for a skillful user to determine the sensitive threshold, but it is very difficult for a general user to determine the sensitive threshold. Further, since a measuring instrument such as a tester needs to be separately prepared as also disclosed in JP 11-320258 A, there is a problem in that work performed until the start of electrical discharge machining is cumbersome.